Apparatus and a method for non-contact electrical testing of printed circuit boards, solid state display devices, integrated circuits and other substrates with traces that connect together components of a circuit, using two modulated charged particle beams. The apparatus includes two sources of beams, electrodes to modulate the beams, optics to focus the beams and deflection coils to deflect the beams over a large area. The apparatus also has an enclosure around the optics and the deflection coils of magnetically soft material. A surrounding solenoid excitation coil creates an almost uniform axial magnetic field within the magnetic enclosure. A detection system for detecting the voltage contrast signals, including suitable signal processing system is also provided. The use of two beams simultaneously allows fast, direct measurement of impedance parameters. By selecting appropriate beam modulation frequencies, the sensitivity to a certain kind of defect can be selectively increased.
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U.S. Patent Classes & Classifications Covered in this listing:
Class 250: Radiant Energy
This class provides for all methods and apparatus for using, generating, controlling or detecting radiant energy, combinations including such methods or apparatus, subcombinations of same and accessories therefore not classifiable elsewhere.
Subclass 305: ELECTRON ENERGY ANALYSIS Subclass 306: INSPECTION OF SOLIDS OR LIQUIDS BY CHARGED PARTICLES Subclass 311: Electron microscope type Subclass 492.1: IRRADIATION OF OBJECTS OR MATERIAL Subclass 492.2: Irradiation of semiconductor devices Subclass 492.22: Pattern control